Re: Why does Gnus article-moving act like a fetch of new news?

[Karl Fogel]

On 03 May 2021, Eric Abrahamsen wrote:
> I thought this was worth looking into more closely, and I'm 
> getting
> closer to figuring out the problem.

[...distant cheering from over the horizon...]

> What we really need is to update the "active" number for the 
> receiving
> group -- that's Gnus' final authoritative figure for how many 
> articles
> are in the group, and if it's not updated then we see Karl's 
> situation
> where you enter the receiving group and don't see the moved 
> articles,
> until you do a full refresh of the group.
>
> The calls to `gnus-group-get-new-news-this-group' make the world 
> right
> only because they end up calling 
> `gnus-get-unread-articles-in-group',
> which updates the group's active number (in addition to a bunch 
> of other
> stuff).
>
> What I'm trying to figure out now is, what's the minimum amount 
> of code
> we can run that does this work, without running a whole bunch of 
> other
> unwanted processes. We can't just set the group's active number
> directly, because we need to check the cache and the agent, and 
> update
> the *Group* buffer, etc., as part of that. So we'll need some
> combination of the "larger" functions, invoked properly, but I 
> haven't
> figured out yet exactly how that will work.
>
> But anyway, the mystery is clearing.

Thank you so much for looking further into this.  Your reasoning & 
questions above seem exactly right to me.  Knowing this 
"combination of the 'larger' functions, invoked properly" would be 
a good thing, and I think might be of general utility in the Gnus 
code.  Surely this isn't the only place where a group needs to be 
told that its article set has changed and that it needs to refresh 
itself in a local-only way.

By the way, I received your message twice, with two separate 
Message-ID headers:

 Message-ID: <87v97zsfod.fsf@ericabrahamsen.net>

 Message-ID: <87tunjsfnm.fsf@ericabrahamsen.net>

Letting you know just in case that's a manifestation of some kind 
of message-sending buglet.  (Since I was an explicit recipient in 
the headers, along with emacs-devel, I wondered if maybe your MUA 
or MDA somehow generates a distinct message, with its own 
Message-ID, for each recipient, instead of all recipients getting 
the same message.)

Best regards,
-Karl